Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using a diary (electronic or paper). By definition, all solicited local AEs occurring from the time of first vaccination were considered related to trial vaccination. For solicited systemic AEs, the Investigator assessed the relationship between trial vaccine and each occurrence of each AE.

Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using a diary (electronic or paper). Intensity of solicited local AEs and solicited systemic AEs were graded per the FDA Toxicity Grading Scale at Grades 1-3, where higher grades indicate a worse outcome.

Solicited local AEs (injection site pain, redness, swelling, and itching) and solicited systemic AEs (fever, headache, fatigue, chills, myalgia, arthralgia, nausea/vomiting, and diarrhea) were recorded on the day of vaccination and the following 7 days using a diary (electronic or paper). Duration is calculated as consecutive days with a respective solicited AE regardless of the grade of the AE. AEs ongoing after day 8 are included.

Diaries were used for collection of unsolicited AEs on each vaccination day and the following 28 days. In addition, participants received a prompt (by e.g., a phone call or text message) to verify whether the participants had any health concerns since the last visit. The Investigator assessed the relationship between trial vaccine and each occurrence of each AE.

Diaries were used for collection of unsolicited AEs on each vaccination day and the following 28 days. In addition, participants received a prompt (by e.g., a phone call or text message) to verify whether the participants had any health concerns since the last visit. The Investigator made an assessment of intensity for each AE reported during the trial and assigned it to one of the following categories: * Mild: an event that was easily tolerated by the participant, causing minimal discomfort and not interfering with everyday activities. * Moderate: an event that caused sufficient discomfort to interfere with normal everyday activities. * Severe: an event that prevented normal everyday activities.

An SAE was defined as any untoward medical occurrence that, at any dose: * Resulted in death. * Was life-threatening. * Required inpatient hospitalization or prolongation of existing hospitalization. * Resulted in persistent disability/incapacity. * Was a congenital anomaly/birth defect in the offspring of the participant. * Was an important medical event. The Investigator assessed the relationship between trial vaccine and each occurrence of each AE.

AESIs included: * AEs with a suspected immune-medicated etiology. * COVID-19 disease. * Other AEs relevant to SARS-CoV-2 vaccine development or the target disease. Participants who became unblinded and/or received a licensed/authorized vaccine were censored at the day after unblinding or at the day after receiving the licensed/authorized vaccine, whichever was earlier. The Investigator assessed the relationship between trial vaccine and each occurrence of each AE.

As measured by enzyme-linked immunosorbent assay (ELISA). In participants not exposed to SARS-CoV-2 before the trial seroconversion was defined as any increase in titer in antibodies against SARS-CoV-2 RBD versus baseline. Participants who received a licensed/authorized vaccine were censored at the day after receiving the licensed/authorized vaccine.

As measured by ELISA. The SARS-CoV-2 spike RBD protein-specific antibodies are expressed as GMT (geometric mean of reciprocal duplicate dilutions). Concentration/titers marked as below the lower limit of quantification (LLOQ) were arbitrary replaced by half of the LLOQ for GMT computations purpose. Participants who received a licensed/authorized vaccine were censored at the day after receiving the licensed/authorized vaccine.

As measured by an activity assay. In participants not exposed to SARS-CoV-2 before the trial, seroconversion was defined as any increase in titer in SARS-CoV-2 neutralizing antibodies versus baseline. Participants who received a licensed/authorized vaccine were censored at the day after receiving the licensed/ authorized vaccine.

The SARS-CoV-2 neutralizing antibodies are expressed as GMT (geometric mean of reciprocal duplicate dilutions). Concentration/titers marked as below the lower limit of quantification (LLOQ) were arbitrary replaced by half of the LLOQ for GMT computations purpose. Participants who received a licensed/authorized vaccine were censored at the day after receiving the licensed/authorized vaccine.